Tropical Cyclone Genesis in the Western North Pacific

Abstract

The author has recently completed a global analysis of tropical cyclone genesis (Gray, 1975a). This paper applies the results of that study to a more detailed analysis of tropical cycline genesis in the western North Pacific and of the variation in the seasonal climatology of genesis location and frequency. The first part of this paper presents statistical information on the seasonal frequency of tropical cyclone genesis and discusses the major physical requirements of genesis. The second part of this paper shows how these hypothesized genesis requirements are specified by the product of six seasonally averaged meteorological parameters. The last part of this paper shows how well the product of these seasonally averaged parameters is related to cyclone genesis location and frequency. A cyclone genesis forecast index is proposed. 1 1 Tropical cyclones are divided into two categories based on their maximum sustained low level winds: 1) tropical storms with speeds between 34 and 63 knots; and 2) typhoons with speeds greater than 63 knots.